1. Field of the Invention
The present invention relates to HVAC (heating, ventilation, and air conditioning) methods and systems for improving fuel economy and emissions of hybrid vehicles during mild ambient conditions.
2. Background Art
A typical HVAC system of a hybrid vehicle does not have the necessary inputs, processing power, and control strategies to make intelligent decisions as to when to turn the A/C (air conditioning) compressor of the vehicle off in order to improve fuel economy and emissions. That is, the typical HVAC system of a hybrid vehicle is not able to make an intelligent decision as to when the engine of the vehicle can be turned off in order to turn off the A/C compressor while the vehicle is at idle. Similarly, the typical HVAC system of a hybrid vehicle is not able to make an intelligent decision as to when to turn the A/C compressor off (without the engine of the vehicle being turned off) while the vehicle is being driven.
As such, a problem associated with hybrid vehicles having typical HVAC systems can be broken down into two operating conditions: 1) at idle (i.e., while the vehicle is at a stop); and 2) while driving (i.e., while the vehicle is being driven).
In the first operating condition in which the vehicle is at idle, a hybrid vehicle operates its engine whenever the A/C compressor has been requested in order to provide the cooling power necessary in the event it is required. Also, the A/C compressor is always requested when the HVAC system is in automatic mode whether or not the A/C compressor is required for comfort. The engine of the hybrid vehicle is operated (i.e., turned on) while the vehicle is at idle because, as indicated above, the HVAC system of the vehicle is not able to make an intelligent decision to turn the engine off (and thus turn off the A/C compressor) to improve fuel economy and emissions.
In the second operating condition in which the vehicle is being driven, a hybrid vehicle operates the A/C compressor in order to provide the cooling power necessary in the event it is required. Also, the A/C compressor is always requested when the HVAC system is in automatic mode whether or not the A/C compressor is required for comfort. The A/C compressor is operated (i.e., turned on) while the vehicle is being driven because, as indicated above, the HVAC system of the vehicle is not able to make an intelligent decision to turn the A/C compressor off (while the engine remains on and operated) to improve fuel economy and emissions.